Earth authorities are completely unprepared for the arrival of alien visitors and worried humans should ready themselves by watching a groundbreaking documentary, the film's director boasts.

Danish director Michael Madsen takes a tough line promoting "The Visit", which is subtitled "An Alien Encounter" and competing in the World Documentary category at the Sundance Film Festival.

Intriguingly, the movie is filmed from the perspective of the first alien arrivals -- with a series of experts and authority figures talking to the camera as if to welcome our new extraterrestrial friends.

"If this happens you should go to watch this film, this is a manual for this," the 43-year-old Madsen told AFP in an interview.

Rather than a "Close Encounters"-style fictional Hollywood epic, Madsen says his film is intended as a serious examination of how humankind should react in the event of an alien arrival.

Surprisingly, he claims the United Nations doesn't have a plan for its response to the arrival of extra-terrestrials, even if they have discussed it -- a fact he describes as "worrying."

In the movie the filmmaker interviews experts from NASA, the UN Office for Outer Space Affairs (which does exist, based in Vienna) and the SETI or Search for Extraterrestrial Intelligence Institute.

Madsen said the film -- intended as the second part of a trilogy which started with his 2010 movie "Into Eternity" -- was "a way of thinking about and exploring this world, this reality."

Not for him UFO films. "If I were to have something with UFOs, it would run into, in my mind, the problem of witnesses talking about subjective things," he explained.

"I'm not interested in that type of film," added the cerebral filmmaker.

- Kubrick's 'Space Odyssey 2001' -

"I like (Stanley) Kubrick's '(Space Odyssey) 2001,' but that's on the grounds that .. he was trying to create a new type of film, a myth, and that intention I find very interesting."

His film also includes a former British government spokeswoman thrashing out exactly how authorities would handle the situation; what they would tell the media and how to avoid mass panic.

They ponder who would be the best person to represent the human race, to talk to the alien.

One answer, somewhat improbably, is BBC wildlife documentary broadcaster Sir David Attenborough. "Everyone trusts him," explains an official.

In reality it would be more likely to be someone from the UN outer space office, whose chief is shown in an orange space suit delving into the impenetrable darkness of the alien spacecraft.

The film does include some discussion of souls, although little directly about religion. Asked about this, Madsen says major world deity-based religions would be in a pickle.

"For some religions it will be devastating. Christianity would be in deep trouble," said the Dane, who describes himself as atheist.

At the world premiere at Sundance, one audience member asked why almost everyone in the documentary is white European, when tackling such a global issue.

Madsen did not see the problem. "After all it is the white people going to space, or has been historically so it is a part of western civilization," he told AFP.

He added that, his priority as a filmmaker was satisfying his own interests.

"You can only make films for yourself, in the sense that if it doesnt interest you .. I don't believe there is any chance of anything interesting coming out of it.

"It's of course not a guarantee," he added.